Cryogenic fluid systems are used in a wide variety of applications, commonly where transport and handling of a material in a liquid state rather than a gaseous state is desired. In recent years, cryogenic fluid systems in the field of internal combustion engines have received increasing interest. Combustible hydrocarbon fuels such as liquefied natural gas (LNG), liquid propane (LP), and still others are known to provide certain advantages over traditional hydrocarbon fuels such as gasoline and diesel, notably with respect to emissions. Economics and resource availability are also factors driving increased attention to technology in this area.
In a typical design a vessel contains a liquefied fuel such as LNG, and is equipped with an apparatus such as a vaporizer or evaporator to transition the fuel from a liquid form to a gaseous form for supplying to cylinders in an engine for combustion. Various systems have been proposed that provide submerged or partially submerged pumps to convey the cryogenic liquid fuel from the storage vessel to the vaporizer equipment. Various challenges are attendant to operating pumps and the like inside of a closed cryogenic storage vessel, however, U.S. Pat. No. 6,129,529 relates to a submersible motor driven pump and drive coupling, with the pump being designed so that liquefied petroleum gas is passed through a motor assembly to cool and lubricate the motor assembly.